1. Field of the Invention
This invention relates to a valve driving apparatus which drives a valve element to control the flow of intake gas or exhaust gas of an internal combustion engine.
2. Description of the Related Art
An electromagnetic valve drive-apparatus controlling the opening and closing of valves by electromagnetic force is known as an apparatus driving valve bodies such as intake valves or exhaust valves which control the flow of intake gas or exhaust gas of an internal combustion engine. This apparatus does not control the valve opening and closing by a cam which is rotatably driven by a crankshaft, but is capable of controlling the valve opening and closing and its timing regardless of the cam configuration and cam rotational speed. However, by increasing the opening and closing speed of the valve, the valve is liable to collide with a surrounding member when the valve seats and, as a result, problems arise, such as abrasion of the valve and its surrounding member and the generation of impulse sounds. For example, an apparatus disclosed in Japanese Patent Kokai No. 10-141028 is provided with an air damper mechanism in the valve driving apparatus in order to reduce shocks during valve seating, thereby solving these problems. However, this valve driving apparatus has a complex structure, thereby creating a new problem.
Also, the valve driving apparatus in which the valves are driven by electromagnetic force needs a power supply to drive the apparatus, and conservation of the power consumption is also required. The apparatus which is disclosed in Japanese Patent Kokai No.8-189315 attempts to conserve power by changing the valve travel distance according to the internal combustion engine driving condition. However, the reduction of the supplied power has caused new problems such as reduced driving force and decreased response characteristics of valve opening and closing.
Furthermore, in the apparatus which is disclosed in Japanese Patent No. 2,772,569, the valve driving force has been increased by arranging a plurality of fixed magnetic poles and controlling the current magnitude supplied to the energizing coil. However, this apparatus has caused the structure to become complex and an increase of power consumption.
As discussed above, the conventional electromagnetic valve driving apparatus which attempts to reduce the shock of the valve when the valve is seated requires a complex structure and increases power consumption in order to precisely control valve movement. Further, with regard to the conventional valve driving apparatus which applies soft ferromagnetic iron material to the moving element, it is also a problem to align the valve to a predetermined position when power to the valve driving apparatus is not applied.
The present invention has been devised in view of the foregoing problems and an object of the invention is to provide an electromagnetic force driven apparatus whereby the structure is simple and the valve seating shock is reduced. Further, valve control is precisely executed with low power consumption, thereby enabling the valve to be placed at a predetermined position when power to the valve driving apparatus is not applied.
The objects of the present invention is to simplify the structure of a valve driving apparatus and to reduce the shock when the valve is seated.
The valve driving apparatus of the present invention is a valve driving apparatus for deriving a valve element controlling intake gas flow or exhaust gas flow of an internal combustion engine. A magnetized path member comprises a magnetic flux generating element in which an electromagnetic coil is wound to generate magnetic flux and a magnetic field generating element comprising at least two pole members to distribute the magnetic flux to form at least one magnetic field. A magnetizing member moves within the magnetic field in cooperation with a valve rod formed integrally with the valve element. The member has two magnetized surfaces with mutually different polarities. A current supply supplies a driving current to the electromagnetic coil corresponding to the poles of either a valve opening direction or a valve closing direction of the valve element.